The present invention relates to a positive photosensitive composition for use in the production of a semiconductor such as IC, in the production of a circuit board such as liquid crystal and thermal head and in other photofabrication processes. More specifically, the present invention relates to a positive photosensitive composition suitable for use in a case where an exposure light source used is a far ultraviolet beam of 250 nm or less.
A positive photoresist composition commonly used is a composition comprising an alkali-soluble resin and a naphthoquinonediazide compound as a photosensitive material. Examples thereof include a xe2x80x9cnovolak-type phenol resin/naphthoquinonediazide-substituted compoundxe2x80x9d described in U.S. Pat. Nos. 3,666,473, 4,115,128 and 4,173,470 and a xe2x80x9cnovolak resin comprising cresol-formaldehyde/trihydroxybenzophenone-1,2-naphthoquinonediazide sulfonic acid esterxe2x80x9d as a most typical composition, described in L. F. Thompson, Introduction to Microlithography, No. 2, 19, pp. 112-121, ACS Publishing.
In these positive photoresists fundamentally comprising a novolak resin and a quinonediazide compound, the novolak resin exhibits high resistance against plasma etching and the naphthoquinonediazide compound acts as a dissolution inhibitor. The naphthoquinonediazide generates a carboxylic acid on irradiation of light and loses its dissolution inhibiting ability to thereby elevate the alkali solubility of the novolak resin.
From this viewpoint, a large number of positive photoresists comprising a novolak resin and a naphthoquinonediazide-base photosensitive material have heretofore been developed and used in practice, and satisfactory results can be obtained in the working for a line width of approximately from 0.8 to 2 xcexcm.
However, integrated circuits are being more and more intensified in the integration degree and the production of a semiconductor substrate such as VLSI requires working of an ultrafine pattern comprising lines having a width of a half micron or less.
According to one of known techniques for achieving miniaturization of a pattern, a resist pattern is formed using an exposure light source having a shorter wavelength. This technique can be described using the following Rayleigh""s formula showing the resolution R (line width) of an optical system:
R=kxc2x7xcexk/NA
(wherein xcex is a wavelength of the exposure light source, NA is a numerical aperture of the lens and k is a process constant). As is apparent from this formula, a higher resolution, namely, a smaller R value can be obtained by reducing the wavelength xcex of the exposure light source.
For example, in the production of a DRAM having an integration degree up to 64 M bits, the i beam (365 nm) of a high-pressure mercury lamp is used at present as the light source. In the mass production of 256-M bit DRAMs, use of a KrF excimer laser (248 nm) in place of the i-line has been studied. Further, for the purpose of producing DRAMs having an integration degree of 1 G bits or more, a light source having a further shorter wavelength has been investigated. To this effect, an ArF excimer laser (193 nm), an F2 excimer laser (157 nm), an X ray, an electron beam and the like are considered to be effective (see, Takumi Ueno et al., Tanpacho Photoresist Zairyo-ULSI Ni Muketa Bisai Kako-(Short Wavelength Photoresist Material-Fine Working Toward ULSI-), Bunshin Shuppan (1988).
When a conventional resist comprising a novolak resin and a naphthoquinonediazide compound is used for the pattern formation by photolithography with a far ultraviolet ray or excimer laser beam, the novolak resin and naphthoquinonediazide compound exhibit strong absorption in the far ultraviolet region and the light scarcely reaches the bottom of resist, as a result, the resist has low sensitivity and only a tapered pattern can be obtained.
One of the techniques for solving this problem is the chemical amplification-type resist composition described in U.S. Pat. No. 4,491,628 and European Patent No. 249,139. The chemical amplification-type positive resist composition is a pattern formation material which generates an acid in the exposed area on irradiation of radiation such as far ultraviolet ray and due to the reaction using the acid as a catalyst, differentiates solubility in a developer between the area irradiated with the active radiation and the non-irradiated area to form a pattern on a substrate.
Examples thereof include combinations of a compound capable of generating an acid by photolysis with an acetal or O,N-acetal compound (see, JP-A-48-89003 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d), with an ortho ester or amide acetal compound (JP-A-51-120714), with a polymer having an acetal or ketal group on the main chain (JP-A-53-133429), with an enol ether compound (JP-A-55-12995), with an N-acyliminocarbonic acid compound (JP-A-55-126236), with a polymer having an ortho ester group on the main chain (JP-A-56-17345), with a tertiary alkyl ester compound (JP-A-60-3625), with a silyl ester compound (JP-A-60-10247) or with a silyl ether compound (JP-A-60-37549, JP-A-60-121446). These combinations in principle have a quantum yield exceeding 1 and therefore exhibit high photosensitivity.
A system which decomposes by heating in the presence of an acid and is alkali-solubilized is also used and examples thereof include combinations of a compound capable of generating an acid on exposure with an ester or carbonic acid ester compound having a tertiary or secondary carbon (e.g., tert-butyl, or 2-cyclohexenyl) described, for example, in JP-A-59-45439, JP-A-60-3625, JP-A-62-229242, JP-A-63-27829, JP-A-63-36240, JP-A-63-250642, JP-A-5-181279, Polym. Eng. Sce., Vol. 23, page 1012 (1983), ACS. Sym., Vol. 242, page 11 (1984), Semiconductor World, November, 1987, page 91, Macromolecules, Vol. 21, page 1475 (1988), and SPIE, Vol. 920, page 42 (1988), with an acetal compound described, for example, in JP-A-4-219757, JP-A-5-249682 and JP-A-6-65332, or with a tert-butyl ether compound described, for example, in JP-A-4-211258 and JP-A-6-65333.
Such systems are mainly composed of a resin having a basic skeleton of poly(hydroxystyrene) which is small in the absorption in the region of 248 nm and therefore, when the exposure light source is a KrF excimer laser, they have high sensitivity and high resolution and are capable of forming a good pattern. Thus they can form good systems as compared with conventional naphthoquinonediazide/novolak resin systems.
However, when the light source has a still shorter wavelength, for example, when the exposure light source used is an ArF excimer laser (193 nm), the above-described chemical amplification systems are yet deficient because the compound having an aromatic group substantially has large absorption in the region of 193 nm. As a polymer having small absorption in the 193 nm region, in J. Vac. Sci. Technol., B9, 3357 (1991), the use of poly(meth)-acrylate is described. However, this polymer has a problem in that the resistance against dry etching which is commonly performed in the production process of semi-conductors is low as compared with conventional phenol resins having aromatic groups.
In Proc. of SPIE, 1672, 66 (1922), it is reported that polymers having alicyclic groups exhibit the dry etching resistance on the same level as that of the compounds having aromatic groups and at the same time, have small absorption in the 193 nm region. The use of these polymers has been aggressively studied in recent years. Specific examples thereof include the polymers described, for example, in JP-A-4-39665, JP-A-5-80515, JP-A-5-265212, JP-A-5-297591, JP-A-5-346668, JP-A-6-289615, JP-A-6-324494, JP-A-7-49568, JP-A-7-185046, JP-A-7-191463, JP-A-7-199467, JP-A-7-234511, JP-A-7-252324, JP-A-8-259626, JP-A-9-73173 and JP-A-9-90637. However, these polymers do not always have sufficient dry etching resistance and are disadvantageous in that the synthesis thereof necessitates many steps.
Further, the introduction of the alicyclic group in order to improve the dry etching resistance is accompanied with the decrease in adhesion to a substrate and causes a problem in that peeling off of the resist layer occurs in the pattern after development. In order to solve such a problem, a resin containing a unit having a xcex3-butyrolactone structure is proposed as described in EP-A-856773. Although the adhesion is improved by using the resin, it has only a low acid decomposing property due to the secondary carboxylic acid ester, resulting in decrease in sensitivity and exhibits insufficiently low resolution. Further, since the hydrophobic property of the resist layer increases by the introduction of the alicyclic group, such a resist composition has another problem of the occurrence of development defects.
Therefore, an object of the present invention is to provide a positive photosensitive composition suitable for use of an exposure light source having a wavelength of 250 nm or less, particularly 220 nm or less.
Another object of the present invention is to provide a positive photosensitive composition which provides good sensitivity, resolution, adhesion and resist pattern and exhibits sufficient dry etching resistance when used with an exposure light source having a wavelength of 250 nm or less, particularly 220 nm or less.
Other objects of the present invention will become apparent from the following description.
As a result of intensive investigations made by the inventors on positive photosensitive compositions while taking the properties described above into consideration, it has been found that the objects of the present invention are successfully accomplished by using a resin having a specific alicyclic group described below, to complete the present invention.
Specifically, the present invention comprises a positive photosensitive composition which comprises (A) a compound which generates an acid upon irradiation with an actinic ray or radiation, and (B) a resin having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution and further containing a group having the specific alicyclic structure.
A first embodiment of the positive photosensitive composition according to the present invention includes the following:
(1) a positive photosensitive composition comprising (A) a compound which generates an acid upon irradiation with an actinic ray or radiation, and (B) a resin having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution, wherein the resin contains at least one structure represented by the following formulae (I), (II) and (III): 
wherein R1 and R2, which may be the same or different, each represents a hydrogen atom or an optionally substituted straight-chain, branched chain or cyclic alkyl group, or R1 and R2 may be bonded to each other to form a monocyclic or polycyclic ring which may contain an oxygen atom, a sulfur atom, a nitrogen atom, a ketone bond, an ester bond, an imido bond or an amido bond as a linking group; R3, R4 and R5, which may be the same or different, each represents a hydrogen atom, an optionally substituted straight-chain, branched chain or cyclic alkyl or alkoxy group, or two or more of R3, R4 and R5 may be bonded to each other to form a monocyclic or polycyclic ring which may contain an oxygen atom, a sulfur atom, a nitrogen atom, a ketone bond, an ester bond, an imido bond or an amido bond as a linking group; X represents a single bond or a divalent linking group, or X and either or both of R1 and R2 may be bonded to each other to form a monocyclic or polycyclic ring; Y represents an oxygen atom, a sulfur atom, xe2x80x94NHxe2x80x94, xe2x80x94N(OH)xe2x80x94 or xe2x80x94N(alkyl)-; and n represents an integer of from 1 to 3;
(2) a positive photosensitive composition comprising (A) a compound which generates an acid upon irradiation with an actinic ray or radiation, (B) a resin having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution, and (C) a low molecular weight compound having a molecular weight of 3,000 or less and having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution, wherein the resin (B) and/or the low molecular weight compound (C) contain at least one structure represented by formulae (I), (II) and (III) described in item (1) above;
(3) a positive photosensitive composition as described in item (1) or (2) above, wherein the resin having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution is (D) a resin which contains at least one repeating unit having the structure represented by formula (I), (II) or (III) and a repeating unit having a monoalicyclic or polyalicyclic hydrocarbon moiety;
(4) a positive photosensitive composition as described in item (1), (2) or (3), wherein the monoalicyclic or polyalicyclic hydrocarbon moiety is an adamantane residue;
(5) a positive photosensitive composition as described in any one of items (1) to (4), wherein the resin having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution contains a structure represented by formula (a): 
wherein R1, R2, R3, R4 and R5, and n are the same as defined in formula (I), and R15 represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group or a haloalkyl group;
(6) the positive photosensitive composition as described in any one of items (1) to (5), wherein the resin having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution contains a structure represented by formula (b): 
wherein R1, R2, R3, R4 and R5, and n are the same as defined in formula (I), and R15 represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group or a haloalkyl group;
wherein R15 in formulae a and b are the same as R15 in formula (IV) described later;
(7) a positive photosensitive composition comprising (A) a compound which generates an acid upon irradiation with an actinic ray or radiation, (C) a low molecular weight compound having a molecular weight of 3,000 or less and having a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution, and (E) a resin which is insoluble in water but soluble in an alkaline developing solution, wherein the low molecular weight compound (C) contains at least one structure represented by formulae (I), (II) and (III) described in item (1) above;
(8) a positive photosensitive composition as described in any one of items (1) to (7) above, wherein R1 and R2 each represents a substituent other than a hydrogen atom;
(9) a positive photosensitive composition as described in any one of items (1) to (7) above, wherein the composition further comprises (F) a fluorine-base and/or silicon-base surface active agent;
(10) a positive photosensitive composition as described in any one of items (1) to (7) above, wherein the composition is suitable for exposure using far ultraviolet light having a wavelength of 250 nm or less as an exposure light source; and
(11) a positive photosensitive composition as described in any one of items (1) to (7) above, wherein the composition is suitable for exposure using far ultraviolet light having a wavelength of 220 nm or less as an exposure light source.
A second embodiment of the positive photosensitive composition according to the present invention includes the following:
(1) a positive photosensitive composition comprising (A) a compound which generates an acid upon irradiation with an actinic ray or radiation and (B) a resin having at least one monovalent polyalicyclic group represented by the following formula (Ib) and a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution: 
wherein Ra, Rb, Rc, Rd, Re, Rf and Rg, which may be the same or different, each represents an optionally substituted alkyl, cycloalkyl, alkenyl or alkynyl group, a halogen atom, a cyano group, xe2x80x94R6bxe2x80x94Oxe2x80x94R7b, xe2x80x94R8bxe2x80x94COxe2x80x94Oxe2x80x94R9b, xe2x80x94R10bxe2x80x94COxe2x80x94NR11bR12b or xe2x80x94R13bxe2x80x94Oxe2x80x94COxe2x80x94R14b; R7b and R9b, which may be the same or different, each represents a hydrogen atom, an optionally substituted alkyl, cycloalkyl or alkenyl group or a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution; R11b, R12b and R14b, which may be the same or different, each represents a hydrogen atom, an optionally substituted alkyl, cycloalkyl or alkenyl group, or R11b and R12b may be bonded to each other to form a ring; R6b, R8b, R10b and R13b, which may be the same or different, each represents a single bond, an optionally substituted alkylene, alkenylene or cycloalkylene group; two of Ra to Rg, which are present on the same carbon atom, may represent in combination a carbonyl group (xe2x95x90O) or a thiocarbonyl group (xe2x95x90S); two of Ra to Rg, which are bonded to adjacent carbon atoms, may be bonded to each other to form a double bond between these two carbon atoms; at least two of Ra to Rg may be bonded to each other to form a ring; and the monovalent polyalicyclic group represented by formula (Ib) may be connected to the resin moiety in any position thereof;
(2) a positive photosensitive composition as described in item (1) above, wherein the resin (B) is a resin comprising at least one repeating unit represented by the following formulae (IVb), (Vb) and (VIb) and a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution: 
wherein R15b, R16b and R18b to R20b, which may be the same or different, each represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group or a haloalkyl group; R17b represents a cyano group, xe2x80x94COxe2x80x94OR27b or xe2x80x94COxe2x80x94NR28bR29b; X1b, X2b and X3b, which may be the same or different, each represents a single bond, an optionally substituted divalent alkylene, alkenylene or cycloalkylene group, xe2x80x94Oxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94R30bxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94R31bxe2x80x94, or xe2x80x94COxe2x80x94NR32bxe2x80x94R33bxe2x80x94; R27b represents a hydrogen atom, an optionally substituted alkyl, cycloalkyl or alkenyl group, or a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution; R28b, R29b and R32b, which may be the same or different, each represents a hydrogen atom or an optionally substituted alkyl, cycloalkyl or alkenyl group, or R28b and R29b may be bonded to each other to form a ring; R30b, R31b and R33b, which may be the same or different, each represents a single bond or a divalent alkylene, alkenylene or cycloalkylene group, or a divalent group formed by combining each of these groups with an ether, ester, amido, urethane or ureido group; and Yb represents the polyalicyclic group represented by formula (Ib) described in item (1) above;
(3) a positive photosensitive composition as described in item (1) or (2) above, wherein the resin (B) is a resin which, is decomposed by the action of an acid to increase solubility in an alkaline developing solution and has at least one repeating unit represented by formulae (IVb), (Vb) and (VIb) as described in item (2) above and at least one repeating unit represented by the following formulae (VIIb), (VIIIb) and (IXb): 
wherein R21b, R22b and R24b to R26b, which may be the same or different, each represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group or a haloalkyl group; R23b represents a cyano group, xe2x80x94COxe2x80x94OR27b or xe2x80x94COxe2x80x94NR28bR29b; X4b, X5b and X6b, which may be the same or different, each represents a single bond, an optionally substituted divalent alkylene, alkenylene or cycloalkylene group, xe2x80x94Oxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94R30bxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94R31bxe2x80x94 or xe2x80x94COxe2x80x94NR32bxe2x80x94R33bxe2x80x94; R27b represents a hydrogen atom, an optionally substituted alkyl, cycloalkyl or alkenyl group, or a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution; R28b, R29b and R32b, which may be the same or different, each represents a hydrogen atom or an optionally substituted alkyl, cycloalkyl or alkenyl group, or R28b and R29b may be bonded to each other to form a ring; R30b, R31b and R33b, which may be the same or different, each represents a single bond or a divalent alkylene, alkenylene or cycloalkylene group, or a divalent group formed by combining each of these groups with an ether, ester, amido, urethane or ureido group; and Bb is a group which is decomposed by the action of an acid to increase solubility in an alkaline developing solution;
(4) a positive photosensitive composition as described in any one of items (1) to (3) above, wherein the resin (B) further comprises a carboxy group;
(5) a positive photosensitive composition as described in item (4) above, wherein the resin (B) further comprises at least one repeating unit represented by the following formulae (Xb), (XIb) and (XIIb) each having a carboxy group: 
wherein R34b, R35b and R37b to R39b, which may be the same or different, each represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group or a haloalkyl group; R36b represents a cyano group, a carboxy group, xe2x80x94COxe2x80x94OR40b or xe2x80x94COxe2x80x94 NR41bR42b; X7b, X8b and X9b, which may be the same or different, each represents a single bond, an optionally substituted divalent alkylene, alkenylene or cycloalkylene group, xe2x80x94Oxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Oxe2x80x94COxe2x80x94R43bxe2x80x94, xe2x80x94COxe2x80x94Oxe2x80x94R44bxe2x80x94 or xe2x80x94COxe2x80x94NR45bxe2x80x94R46bxe2x80x94; R40b represents an optionally substituted alkyl, cycloalkyl or alkenyl group; R41b, R42b and R45b, which may be the same or different, each represents a hydrogen atom or an optionally substituted alkyl, cycloalkyl or alkenyl group, or R41b and R42b may be bonded to each other to form a ring; R43b, R44b and R46b, which may be the same or different, each represents a single bond or a divalent alkylene, alkenylene or cycloalkylene group, or a divalent group formed by combining each of these groups with an ether, ester, amido, urethane or ureido group;
(6) a positive photosensitive composition as described in any one of items (1) to (5) above, wherein the composition further comprises a low molecular weight acid-decomposable dissolution inhibiting compound whose solubility in an alkaline developing solution increases by the action of an acid and which has a group capable of being decomposed by the action of an acid and a molecular weight of 3,000 or less;
(7) a positive photosensitive composition as described in any of items (1) to (6) above, wherein the composition is suitable for exposure using far ultraviolet light having a wavelength of 250 nm or less as an exposure light source; and
(8) a positive photosensitive composition as described in item (7) above, wherein the composition is suitable for exposure using far ultraviolet light having a wavelength of 220 nm or less as an exposure light source.